In a conventional three-level power converting apparatus, semiconductor devices, such as switching devices and diodes, constituting a main circuit of each phase configure a single unit, in which the main circuit is configured such that four semiconductor devices including first to fourth semiconductor devices are connected in series between a positive direct current (DC) terminal and a negative DC terminal, a first diode and a second diode are connected in series, an alternating current (AC) terminal is connected to a joint between the second semiconductor device and the third semiconductor device, a neutral point terminal is connected to a joint between the first diode and the second diode, the first diode is connected to a joint between the first semiconductor device and the second semiconductor device, and the second diode is connected to a joint between the third semiconductor device and the fourth semiconductor device. A group of semiconductor devices constituting one unit are arranged on a heat sink portion of a cooling device with short sides of the individual semiconductor devices facing a direction from which cooling air flows, in which the first diode and the second diode with low heat generation loss are disposed in a central area of the heat sink portion of the cooling device, the second semiconductor device and the third semiconductor device with high heat generation loss are disposed on both sides of the first and second diodes, and the first semiconductor device and the fourth semiconductor device whose heat generation loss is lower than that of the second and third semiconductor devices are disposed at both ends of the heat sink portion (refer to Patent Document 1, for example).
Patent Document 1: Japanese Patent Application Publication No. 2003-79162